RCB scored an impressive 2-205 but Kings chased them down with a over to spare making 5-208 with Smith crashing 25 off eight balls.
An explosive innings of 88 from 57 balls by new skipper Faf du Plessis was the foundation of the RCB innings. Virat Kohli, who stepped down as captain after the previous campaign, backed him up with 41no off 29 balls. Dinesh Karthik provided a final flourish smashing an unbeaten 32 off 14 balls.
Rahul Chahar, who conceded 22 off his four overs, was the pick of the bowlers.
Faced with this daunting target Kings were unfazed reaching the mid-point of their innings well-placed at 1-97. Then Shikhar Dhawan and Bhanuka Rajapaksa were both dismissed for 43, off 29 and 22 balls respectively. With Liam Livingstone (19 off 10) going cheaply Kings were left requiring 36 off the last 18 balls.
But it should have worse, as Smith had been dropped on the boundary, a regulation catch, by Anuj Rawat.
Smith punished the miss, taking Mohammed Siraj for three sixes and a four in the 18th over to set up victory.
RCB's attack badly missed Australian T20 World Cup winners Josh Hazlewood and Glenn Maxwell, who are not yet available following the Test tour of Pakistan.
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